Solid-liquid coupling pre-water shutoff fracturing technology for high water cut oil well

Abstract

This invention provides a pre-fracturing water shut-off process for high water-cut oil wells using a solid-liquid coupling method, comprising the following steps: 1) Injecting liquid plugging agent: Injecting liquid plugging agent into the water channel in the target oil well formation, allowing it to penetrate deep into the water channel and cross-link into a gel under formation conditions, deeply sealing the water-flooded channels of old fractures and forming a stress shield in the area, providing a basis for secondary fracturing to redirect the flow; 2) Injecting solid plugging agent: Pushing solid plugging agent as a post-slug to the far end of the sealing area, allowing it to solidify under formation conditions to form an isolation layer, and forming a synergistic sealing system with the liquid plugging agent; 3) Secondary redirecting fracturing: Performing fracturing operations under the action of the synergistic sealing system, utilizing stress shielding and the injected fiber temporary plugging agent to force the hydraulic fractures to redirect, forming new fractures in untouched or poorly utilized oil layers. The water shut-off fracturing process provided by this invention simplifies the construction process, reduces operating costs, and improves the productivity of high water-cut oil wells.

Description

Technical Field

[0001] This invention relates to the field of petroleum extraction technology, and in particular to a pre-fracturing process for solid-liquid coupling in high water-cut oil wells. Background Technology

[0002] High water cut is a common characteristic of reservoirs in the middle and late stages of water-injection development. As the water cut increases, well productivity declines, and development efficiency decreases. To address the high water cut problem, the oil extraction field typically employs two types of techniques: For older high water-cut wells, repeated fracturing is often used, which involves applying high-pressure fluid again to create new fractures in the reservoir or extend existing fractures, thereby restoring or increasing well productivity. For new high water-cut wells, especially those with well-developed natural fractures in the reservoir and where fracturing easily connects to water-bearing layers, water shut-off techniques are often used. This involves injecting plugging agents into the water-producing layers to seal the water phase seepage channels, achieving water control and oil stabilization.

[0003] However, when repeat fracturing old wells using existing technologies, the high-pressure fluid easily extends along the main fracture formed during the initial fracturing, making it difficult to create new fractures in untouched reservoirs. This limits the scope of fracturing. Furthermore, under high water-cut conditions, if water channels are not effectively blocked, fracturing fluid and proppant can easily migrate along the water-bearing fractures. This not only fails to effectively transform the oil layer but also expands and exacerbates water migration, leading to a further increase in water cut. In some cases, this can even result in a significant increase in fluid production after fracturing, but a decrease in oil production. Water shut-off technology suffers from insufficient accuracy in diagnosing water-bearing zones, poor selectivity of chemical plugging agents, easy damage to the oil layer, insufficient temperature and salt resistance of plugging agents, and limited sealing depth, resulting in low water shut-off efficiency and unstable effects. Moreover, existing repeat fracturing technology for old wells and water shut-off technology for high water-cut oil wells are often implemented independently, resulting in long construction cycles, high costs, and insufficient synergistic effects. This fails to address the problem of "water control without oil increase, and oil increase inevitably leading to water increase," making it difficult to achieve efficient development of high water-cut reservoirs. Summary of the Invention

[0004] This invention provides a solid-liquid coupling pre-shutdown fracturing process for high water-cut oil wells, which solves the problem of "water control without oil increase, and oil increase inevitably leading to water increase" caused by the disconnect between water shut-off and fracturing processes in the development of high water-cut oil wells in the prior art.

[0005] This invention provides a pre-fracturing and water shut-off process for solid-liquid coupling in high water-cut oil wells, comprising the following steps: 1) Injection of liquid plugging agent: Liquid plugging agent is injected into the water channel in the formation of the target oil well. The fluidity of the liquid plugging agent allows it to penetrate into the deep part of the water channel and cross-link into a gel under formation conditions, thereby sealing the old fracture water flooding channel at a deep depth and forming a stress shield in the area, providing a basis for subsequent secondary fracturing to achieve a change in direction. 2) Injecting solid plugging agent: After step 1), solid plugging agent is injected into the target formation. The solid plugging agent is pushed to the far end of the sealing area as a post-slug, so that it solidifies under formation conditions to form a high-strength, low-permeability isolation layer, which strengthens the sealing strength of the water flooding channel, prevents the subsequent secondary fracturing fluid from entering the old fracture and scouring the liquid plugging agent, and forms a synergistic sealing system with the liquid plugging agent. 3) Secondary redirection fracturing: Fracturing operations are carried out under the action of a synergistic plugging system. By utilizing stress shielding and the injected fiber temporary plugging agent, the hydraulic fractures are forced to redirect, forming new fractures in unused or poorly utilized oil layers.

[0006] Optionally, the liquid plugging agent is a hydrogel, which is prepared through the following steps: 1) Add the designed amount of injection water to the mixing tank, and then slowly add the modified acrylamide-sodium acrylate copolymer dry powder at a ratio of 0.3%-0.5% while stirring; 2) Control the water temperature at 20-30℃ and stir continuously for 60-90 minutes until the polymer is completely dissolved; 3) Add 0.01%-0.02% sodium thiosulfate by volume of the injected water and continue stirring until homogeneous; 4) Add acetate-sodium acetate buffer solution to adjust the pH of the system to 6.5-7; 5) Let the polymer system stand for 2-4 hours to mature, and at the same time dilute the composite organic delayed crosslinking agent with water at a ratio of 1:(10-15) to obtain a crosslinking agent dilution solution; 6) The liquid plugging agent is obtained by mixing the polymer system and the crosslinking agent dilution at a volume ratio of 100:(2.5-5).

[0007] Optionally, the preparation method of the modified acrylamide-sodium acrylate copolymer includes the following steps: 1) Add the following parts by weight of raw materials to the reaction vessel: 60-70 parts of acrylamide, 15-25 parts of sodium acrylate, 10-20 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 400-450 parts of deionized water, and then stir and mix. 2) Adjust the pH of the system to 7-8 with sodium hydroxide solution, and then purge nitrogen gas into the system for 30-40 minutes to remove dissolved oxygen; 3) At 10-20℃, add ammonium persulfate (0.01%-0.05% of total monomers) and sodium bisulfite (0.01%-0.03% of total monomers) to the system sequentially, then continue to purge with nitrogen gas and continue the reaction for 5-8 hours. 4) Heat to 40-50℃ and keep warm for 2-4 hours to ensure the reaction is complete and obtain polymer blocks; 5) The modified acrylamide-sodium acrylate copolymer is obtained by drying, crushing and sieving the polymer block.

[0008] Optionally, the preparation method of the composite organic delayed crosslinking agent includes the following steps: 1) Add 30-40 parts of deionized water to the reactor; 2) Slowly add 25-35 parts of zirconium oxychloride to deionized water and stir until dissolved; 3) Slowly add 20-25 parts of lactic acid and 5-10 parts of triethanolamine to the system, while controlling the reaction temperature to not exceed 40℃; 4) After the addition is complete, continue stirring and react for 2-3 hours; 5) Add 10-20 parts of deionized water to the system and stir until homogeneous.

[0009] Optionally, the preparation process of the solid plugging agent includes the following steps: 1) Take 80-100 parts of clean water, add 0.4-0.6 parts of xanthan gum, and stir for 20-30 minutes until a uniform suspension is formed; 2) Add 25-35 parts of quartz sand and 8-12 parts of nano-calcium carbonate to the suspension base liquid, and stir at a speed of 700-800 r / min for 10-15 min to obtain a mixed suspension; 3) Slowly add 100 parts of curable resin-coated particles to the mixed suspension and stir at 300-400 r / min for 20-30 min until the particle surface is uniformly coated to obtain solid sealant.

[0010] Optionally, the quartz sand has a mesh size of 70-140 mesh, and the nano-calcium carbonate has a particle size of 50-100 nm.

[0011] Optionally, the preparation process of the curable resin-coated particles is as follows: 1) Take 100 parts of granular aggregate with a particle size of 70-140 mesh, dry it at 100-120℃ to remove surface moisture, and cool it to room temperature for later use. 2) Take 0.5-1 part of silane coupling agent KH-550 and mix it with anhydrous ethanol at a mass ratio of 1:4. Spray the coupling agent after mixing with ethanol evenly on the surface of aggregate particles and let it stand for 30 minutes. 3) Take 12-18 parts of phenolic resin, heat it to 70-80℃, and then take 2-3 parts of hexamethylenetetramine curing agent and mix it evenly with the resin. 4) Mix the resin mixture with the surface-treated granular aggregate until homogeneous; 5) Dry the coated granules at 90-100℃ until the resin granules no longer stick together, and you will get curable resin coated granules.

[0012] Optionally, the injection volume ratio of liquid plugging agent to solid plugging agent is 60:1, and the injection volume of solid plugging agent accounts for 40% of the target fracture volume.

[0013] Optionally, the injection of liquid plugging agent, the injection of solid plugging agent, and the secondary diversion fracturing are continuous operations that do not require tripping the tubing string.

[0014] Optionally, the solid-liquid coupling pre-plugging fracturing technology for high water-cut oil wells is suitable for repeated fracturing stimulation of old high water-cut wells and for commissioning of new high water-cut wells.

[0015] The beneficial effects of the solid-liquid coupling pre-fracturing and water shut-off process for high water-cut oil wells provided by this invention are as follows: 1. A composite system combining deep penetration of liquid plugging agent and reinforcement of solid plugging agent is adopted. The liquid plugging agent achieves deep sealing and stress shielding at depths of over 80m, while the solid plugging agent forms a low-permeability isolation layer with a permeability of ≤1mD. The high sealing rate solves the problem of single liquid plugging agent being easily washed away by fracturing fluid and failing to seal, providing dual protection for water control effect.

[0016] 2. By integrating solid-liquid plugging and secondary deflection fracturing processes, there is no need to trip the tubing string. First, the water channel is cut off by plugging agent, and then stress shielding and fiber temporary plugging are used to force the fracture to deflect into the unused oil layer. The deflection success rate is high, which solves the problem of traditional technology that only plugs water without increasing oil and that fracturing inevitably increases water.

[0017] 3. The plugging agent system provided by this invention has good temperature resistance and salinity resistance, and is suitable for complex reservoir environments such as high temperature, high salinity, low porosity and low permeability. Moreover, the integrated process simplifies the construction process, reduces operating costs and reservoir damage, and significantly improves the productivity, effective period of measures and input-output ratio of high water-cut oil wells. It provides reliable technical support for stable production and efficiency improvement and extended development life of complex high water-cut oil reservoirs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram illustrating the technical principle of the solid-liquid coupling pre-shutdown fracturing process provided by the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of the present invention.

[0021] This invention provides a pre-fracturing and water shut-off process for solid-liquid coupling in high water-cut oil wells, comprising the following steps: 1) Injection of liquid plugging agent: Liquid plugging agent is injected into the water channel in the formation of the target oil well. The fluidity of the liquid plugging agent allows it to penetrate into the deep part of the water channel and cross-link into a gel under formation conditions, thereby deeply sealing the water flooding channel of the old fracture and forming a stress shield in the area, providing a basis for subsequent secondary fracturing to achieve a change in direction.

[0022] 2) Injecting solid plugging agent: After step 1), solid plugging agent is injected into the target formation. The solid plugging agent is pushed to the far end of the sealing area as a post-slug, so that it solidifies under formation conditions to form a high-strength, low-permeability isolation layer, which strengthens the sealing strength of the water flooding channel, prevents the subsequent secondary fracturing fluid from entering the old fracture and eroding the liquid plugging agent, and forms a synergistic sealing system with the liquid plugging agent.

[0023] 3) Secondary redirection fracturing: Fracturing operations are carried out under the action of a synergistic plugging system. By utilizing stress shielding and the injected fiber temporary plugging agent, the hydraulic fractures are forced to redirect, forming new fractures in unused or poorly utilized oil layers.

[0024] The essence of the solid-liquid coupling pre-shutdown fracturing process for high water-cut oil wells provided by this invention is to first control the water channel and then create new oil fractures, integrating water shut-off and fracturing operations into one, so as to solve the problem that fracturing easily increases water and water shut-off does not increase oil.

[0025] During water shut-off fracturing operations, a liquid plugging agent is first injected into the water channel. This liquid plugging agent serves two purposes: firstly, it deeply seals the water-flooded channels in the old fractures; secondly, it creates a stress shield. The liquid plugging agent has good fluidity upon injection, allowing it to penetrate deep into the formation along the water channel. Subsequently, at formation temperatures, it cross-links into a gel, forming a high-strength gel that blocks the flow path of water from the injection well to the oil well. The gel occupies the original fracture space. Due to its high elastic modulus, it can withstand some of the geostress, increasing the fracturing pressure in the original fracture direction. This stress shield allows subsequent fracturing fractures to actively deflect, preventing them from extending along the original fracture during repeated fracturing, thus forcing the hydraulic fractures to turn in other directions during subsequent fracturing.

[0026] After the liquid plugging agent gels, a solid plugging agent is injected. Under formation conditions, the solid plugging agent solidifies to form a hard plug with a compressive strength far exceeding that of the liquid gel. This hardened plug can withstand the high-pressure erosion of subsequent fracturing fluids, and its extremely low permeability after solidification effectively prevents fracturing fluid from entering the original water channel. The liquid plugging agent is injected first, followed by the solid plugging agent. The solid plugging agent acts as a "post-plug," moving forward under the impetus of the injected liquid and eventually being pushed to the far end of the plugging zone. The solid plugging agent forms a high-strength isolation layer at the far end, while the liquid gel fills the proximal and deeper layers. When subsequent fracturing fluid enters, it first encounters the high-strength isolation layer formed by the solid plugging agent, preventing it from eroding the internal liquid gel and thus protecting the integrity of the entire plugging system.

[0027] After both liquid and solid plugging agents are injected, they form a sealing system, and fracturing operations can then commence. At the start of fracturing, the fracturing fluid first enters the formation, seeking the direction of least resistance. Since the original fracture direction has become a high-stress zone, the fracturing fluid cannot extend along the original fracture and can only extend into the untouched oil-bearing layer area with lower stress, thus forming new fractures. During fracturing, a fiber-based temporary plugging agent is injected; commercially available temporary plugging agents are acceptable. After entering the fracture with the fracturing fluid, the fiber-based temporary plugging agent forms a bridging blockage at the fracture entrance or inside the fracture, instantaneously increasing local pressure and further forcing the fracturing fluid to change direction. The role of the fiber-based temporary plugging agent is to "reinforce" the stress shielding effect, especially suitable for situations with insufficient stress shielding or complex fracture morphology. The newly formed fractures penetrate previously untouched oil-bearing layer areas, which have high oil saturation. Fractures provide pathways for oil and gas to flow from the reservoir matrix into the wellbore. Meanwhile, because the water channel has been effectively blocked by solid and liquid plugging agents, fracturing fluid and formation water will not enter the oil layer, resulting in a significant increase in oil production without an increase in water production.

[0028] Furthermore, the liquid plugging agent is a hydrogel, which is prepared through the following steps: 1) Add the designed amount of injection water to the mixing tank, and then slowly add the modified acrylamide-sodium acrylate copolymer dry powder at a ratio of 0.3%-0.5% while stirring; 2) Control the water temperature at 20-30℃ and stir continuously for 60-90 minutes until the polymer is completely dissolved; 3) Add 0.01%-0.02% sodium thiosulfate by volume of the injected water and continue stirring until homogeneous; 4) Add acetate-sodium acetate buffer solution to adjust the pH of the system to 6.5-7; 5) Let the polymer system stand for 2-4 hours to mature, and at the same time dilute the composite organic delayed crosslinking agent with water at a ratio of 1:(10-15) to obtain a crosslinking agent dilution solution; 6) The liquid plugging agent is obtained by mixing the polymer system and the crosslinking agent dilution at a volume ratio of 100:(2.5-5).

[0029] Because liquid plugging agents have low viscosity at room temperature, they are prepared and injected on-site to avoid premature gelation.

[0030] Furthermore, the preparation method of the modified acrylamide-sodium acrylate copolymer includes the following steps: 1) Add the following parts by weight of raw materials to the reaction vessel: 60-70 parts of acrylamide, 15-25 parts of sodium acrylate, 10-20 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 400-450 parts of deionized water, and then stir and mix. 2) Adjust the pH of the system to 7-8 with sodium hydroxide solution, and then purge nitrogen gas into the system for 30-40 minutes to remove dissolved oxygen; 3) At 10-20℃, add ammonium persulfate (0.01%-0.05% of total monomers) and sodium bisulfite (0.01%-0.03% of total monomers) to the system sequentially, then continue to purge with nitrogen gas and continue the reaction for 5-8 hours. 4) Heat to 40-50℃ and keep warm for 2-4 hours to ensure the reaction is complete and obtain polymer blocks; 5) The modified acrylamide-sodium acrylate copolymer is obtained by drying, crushing and sieving the polymer block.

[0031] Furthermore, the preparation method of the composite organic delayed crosslinking agent includes the following steps: 1) Add 30-40 parts of deionized water to the reactor; 2) Slowly add 25-35 parts of zirconium oxychloride to deionized water and stir until dissolved; 3) Slowly add 20-25 parts of lactic acid and 5-10 parts of triethanolamine to the system, while controlling the reaction temperature to not exceed 40℃; 4) After the addition is complete, continue stirring and react for 2-3 hours; 5) Add 10-20 parts of deionized water to the system and stir until homogeneous.

[0032] Furthermore, the preparation process of the solid plugging agent includes the following steps: 1) Take 80-100 parts of clean water, add 0.4-0.6 parts of xanthan gum, and stir for 20-30 minutes until a uniform suspension is formed; 2) Add 25-35 parts of quartz sand and 8-12 parts of nano-calcium carbonate to the suspension base liquid, and stir at a speed of 700-800 r / min for 10-15 min to obtain a mixed suspension; 3) Slowly add 100 parts of curable resin-coated particles to the mixed suspension and stir at 300-400 r / min for 20-30 min until the particle surface is uniformly coated to obtain solid sealant.

[0033] Furthermore, the quartz sand has a mesh size of 70-140 mesh, and the nano-calcium carbonate has a particle size of 50-100 nm.

[0034] Furthermore, the preparation process of the curable resin-coated particles is as follows: 1) Take 100 parts of granular aggregate with a particle size of 70-140 mesh, dry it at 100-120℃ to remove surface moisture, and cool it to room temperature for later use. 2) Take 0.5-1 part of silane coupling agent KH-550 and mix it with anhydrous ethanol at a mass ratio of 1:4. Spray the coupling agent after mixing with ethanol evenly on the surface of aggregate particles and let it stand for 30 minutes. 3) Take 12-18 parts of phenolic resin, heat it to 70-80℃, and then take 2-3 parts of hexamethylenetetramine curing agent and mix it evenly with the resin. 4) Mix the resin mixture with the surface-treated granular aggregate until homogeneous; 5) Dry the coated granules at 90-100℃ until the resin granules no longer stick together, and you will get curable resin coated granules.

[0035] Furthermore, the injection volume ratio of liquid plugging agent to solid plugging agent is 60:1, and the injection volume of solid plugging agent accounts for 40% of the target fracture volume.

[0036] Furthermore, the injection of liquid plugging agent, the injection of solid plugging agent, and the secondary diversion fracturing are continuous operations, without the need to raise or lower the tubing string.

[0037] Furthermore, the solid-liquid coupling pre-plugging fracturing technology for high water-cut oil wells is suitable for repeated fracturing stimulation of old high water-cut wells and for commissioning of new high water-cut wells.

[0038] The present invention will be further described in detail below with reference to specific embodiments.

[0039] Experimental Example 1 Preparation of liquid plugging agent In preparing the liquid plugging agent, the modified acrylamide-sodium acrylate copolymer dry powder and the composite organic delayed crosslinking agent are first prepared.

[0040] The preparation method of the modified acrylamide-sodium acrylate copolymer is as follows: 1) Add the following parts by weight of raw materials to the reaction vessel: 60 parts acrylamide, 15 parts sodium acrylate, 10 parts 2-acrylamide-2-methylpropanesulfonic acid, and 400 parts deionized water, and then stir and mix. 2) Adjust the pH of the system to 7 with sodium hydroxide solution, and then purge nitrogen gas into the system for 30 minutes to remove dissolved oxygen; 3) At 10℃, add 0.01% of ammonium persulfate and 0.01% of sodium bisulfite of total monomers to the system in sequence, and then continue to purge with nitrogen gas for 5 hours. 4) Heat to 40℃ and keep warm for 2 hours to ensure the reaction is complete and obtain polymer blocks; 5) The modified acrylamide-sodium acrylate copolymer is obtained by drying, crushing and sieving the polymer block.

[0041] The preparation method of the composite organic delayed crosslinking agent includes the following steps: 1) Add 30 parts of deionized water to the reactor; 2) Slowly add 25 parts of zirconium oxychloride to deionized water and stir until dissolved; 3) Slowly add 20 parts of lactic acid and 5 parts of triethanolamine to the system, while controlling the reaction temperature to not exceed 40°C; 4) After the addition is complete, continue stirring and react for 2 hours; 5) Add 10 parts of deionized water to the system and stir well.

[0042] The hydroponic gel is prepared through the following steps: 1) Add the designed amount of injection water to the mixing tank, and then slowly add the modified acrylamide-sodium acrylate copolymer dry powder at a ratio of 0.3% while stirring; 2) Control the water temperature at 20℃ and stir continuously for 60 minutes until the polymer is completely dissolved; 3) Add 0.01% sodium thiosulfate by volume of the injected water and continue stirring until homogeneous; 4) Adjust the pH of the system to 6.5 by adding an acetate-sodium acetate buffer solution; 5) Let the polymer system stand for 2 hours to mature, and at the same time dilute the composite organic delayed crosslinking agent with water at a ratio of 1:15 to obtain a crosslinking agent dilution solution; 6) The liquid plugging agent is obtained by mixing the polymer system and the crosslinking agent dilution at a volume ratio of 100:5.

[0043] Preparation of solid plugging agent When preparing solid plugging agents, the first step is to prepare curable resin-coated particles: The preparation process of curable resin-coated particles is as follows: 1) Take 100 parts of quartz sand with a particle size of 70-140 mesh, dry it at 100℃ to remove surface moisture, and cool it to room temperature for later use. 2) Take 0.5 parts of silane coupling agent KH-550 and mix it with anhydrous ethanol at a mass ratio of 1:4. Spray the coupling agent after mixing with ethanol evenly on the surface of aggregate particles and let it stand for 30 minutes. 3) Take 12 parts of phenolic resin, heat it to 70°C, and then take 2 parts of hexamethylenetetramine curing agent and mix it evenly with the resin. 4) Mix the resin mixture with the surface-treated granular aggregate until homogeneous; 5) Dry the coated particles at 90°C until the resin particles no longer stick together to obtain curable resin-coated particles.

[0044] The preparation process of solid plugging agents includes the following steps: 1) Take 80 parts of water, add 0.4 parts of xanthan gum, and stir for 20 minutes until a uniform suspension is formed; 2) Add 25 parts of quartz sand and 8 parts of nano-calcium carbonate to the suspension base liquid, and stir at 700 r / min for 10 min to obtain a mixed suspension. 3) Slowly add 100 parts of curable resin-coated particles to the mixed suspension and stir at 300 r / min for 20 min until the particle surface is uniformly coated to obtain solid blocker.

[0045] Experiment Example 2 Preparation of liquid plugging agent In preparing the liquid plugging agent, the modified acrylamide-sodium acrylate copolymer dry powder and the composite organic delayed crosslinking agent are first prepared.

[0046] The preparation method of the modified acrylamide-sodium acrylate copolymer is as follows: 1) Add the following parts by weight of raw materials to the reaction vessel: 70 parts acrylamide, 25 parts sodium acrylate, 20 parts 2-acrylamide-2-methylpropanesulfonic acid, and 450 parts deionized water, and then stir and mix. 2) Adjust the pH of the system to 8 with sodium hydroxide solution, and then purge nitrogen gas into the system for 40 minutes to remove dissolved oxygen; 3) At 20°C, add 0.05% of the total amount of ammonium persulfate and 0.03% of the total amount of sodium bisulfite to the system in sequence, and then continue to purge with nitrogen gas for 8 hours. 4) Heat to 50℃ and keep warm for 4 hours to allow the reaction to complete and obtain polymer blocks; 5) The modified acrylamide-sodium acrylate copolymer is obtained by drying, crushing and sieving the polymer block.

[0047] The preparation method of the composite organic delayed crosslinking agent includes the following steps: 1) Add 40 parts of deionized water to the reactor; 2) Slowly add 35 parts of zirconium oxychloride to deionized water and stir until dissolved; 3) Slowly add 25 parts of lactic acid and 10 parts of triethanolamine to the system, while controlling the reaction temperature to not exceed 40°C; 4) After the addition is complete, continue stirring and react for 3 hours; 5) Add 20 parts of deionized water to the system and stir until homogeneous.

[0048] The hydroponic gel is prepared through the following steps: 1) Add the designed amount of injection water to the mixing tank, and then slowly add the modified acrylamide-sodium acrylate copolymer dry powder at a ratio of 0.5% while stirring; 2) Control the water temperature at 30℃ and stir continuously for 90 minutes until the polymer is completely dissolved; 3) Add sodium thiosulfate at 0.02% of the injected water volume and continue stirring until homogeneous; 4) Add acetate-sodium acetate buffer solution to adjust the pH of the system to 7; 5) Let the polymer system stand for 4 hours to mature, and at the same time dilute the composite organic delayed crosslinking agent with water at a ratio of 1:10 to obtain a crosslinking agent dilution solution; 6) The liquid plugging agent is obtained by mixing the polymer system and the crosslinking agent dilution at a volume ratio of 100:2.5.

[0049] Preparation of solid plugging agent When preparing solid plugging agents, the first step is to prepare curable resin-coated particles: The preparation process of curable resin-coated particles is as follows: 1) Take 100 parts of quartz sand with a particle size of 70-140 mesh, dry it at 120℃ to remove surface moisture, and cool it to room temperature for later use. 2) Take 1 part of silane coupling agent KH-550 and mix it with anhydrous ethanol at a mass ratio of 1:4. Spray the coupling agent after mixing with ethanol evenly on the surface of aggregate particles and let it stand for 30 minutes. 3) Take 18 parts of phenolic resin, heat it to 80°C, and then take 3 parts of hexamethylenetetramine curing agent and mix it evenly with the resin. 4) Mix the resin mixture with the surface-treated granular aggregate until homogeneous; 5) Dry the coated granules at 100℃ until the resin granules no longer stick together to obtain curable resin-coated granules.

[0050] The preparation process of solid plugging agents includes the following steps: 1) Take 100 parts of water, add 0.6 parts of xanthan gum, and stir for 30 minutes until a uniform suspension is formed; 2) Add 35 parts of quartz sand and 12 parts of nano-calcium carbonate to the suspension base liquid, and stir at 800 r / min for 15 min to obtain a mixed suspension. 3) Slowly add 100 parts of curable resin-coated particles to the mixed suspension and stir at 400 r / min for 30 min until the particle surface is uniformly coated to obtain solid blockage agent.

[0051] Experimental Example 3 Preparation of liquid plugging agent In preparing the liquid plugging agent, the modified acrylamide-sodium acrylate copolymer dry powder and the composite organic delayed crosslinking agent are first prepared.

[0052] The preparation method of the modified acrylamide-sodium acrylate copolymer is as follows: 1) Add the following parts by weight of raw materials to the reaction vessel: 65 parts acrylamide, 20 parts sodium acrylate, 15 parts 2-acrylamide-2-methylpropanesulfonic acid, and 430 parts deionized water, and then stir to mix. 2) Adjust the pH of the system to 7 with sodium hydroxide solution, and then purge nitrogen gas into the system for 30 minutes to remove dissolved oxygen; 3) At 15°C, add 0.03% of the total amount of ammonium persulfate and 0.02% of the total amount of sodium bisulfite to the system in sequence, and then continue to purge with nitrogen gas for 7 hours. 4) Heat to 50℃ and keep warm for 3 hours to ensure the reaction is complete and obtain polymer blocks; 5) The modified acrylamide-sodium acrylate copolymer is obtained by drying, crushing and sieving the polymer block.

[0053] The preparation method of the composite organic delayed crosslinking agent includes the following steps: 1) Add 40 parts of deionized water to the reactor; 2) Slowly add 30 parts of zirconium oxychloride to deionized water and stir until dissolved; 3) Slowly add 22 parts of lactic acid and 7 parts of triethanolamine to the system, while controlling the reaction temperature to not exceed 40°C; 4) After the addition is complete, continue stirring and react for 3 hours; 5) Add 15 parts of deionized water to the system and stir well.

[0054] The hydroponic gel is prepared through the following steps: 1) Add the designed amount of injection water to the mixing tank, and then slowly add the modified acrylamide-sodium acrylate copolymer dry powder at a ratio of 0.4% while stirring; 2) Control the water temperature at 30℃ and stir continuously for 80 minutes until the polymer is completely dissolved; 3) Add sodium thiosulfate at 0.02% of the injected water volume and continue stirring until homogeneous; 4) Add acetate-sodium acetate buffer solution to adjust the pH of the system to 7; 5) Let the polymer system stand for 3 hours to mature, and at the same time dilute the composite organic delayed crosslinking agent with water at a ratio of 1:13 to obtain a crosslinking agent dilution solution; 6) The liquid plugging agent is obtained by mixing the polymer system and the crosslinking agent dilution at a volume ratio of 100:3.

[0055] Preparation of solid plugging agent When preparing solid plugging agents, the first step is to prepare curable resin-coated particles: The preparation process of curable resin-coated particles is as follows: 1) Take 100 parts of quartz sand with a particle size of 70-140 mesh, dry it at 110℃ to remove surface moisture, and cool it to room temperature for later use. 2) Take 0.7 parts of silane coupling agent KH-550 and mix it with anhydrous ethanol at a mass ratio of 1:4. Spray the coupling agent after mixing with ethanol evenly on the surface of aggregate particles and let it stand for 30 minutes. 3) Take 15 parts of phenolic resin, heat it to 80°C, and then take 3 parts of hexamethylenetetramine curing agent and mix it evenly with the resin. 4) Mix the resin mixture with the surface-treated granular aggregate until homogeneous; 5) Dry the coated granules at 100℃ until the resin granules no longer stick together to obtain curable resin-coated granules.

[0056] The preparation process of solid plugging agents includes the following steps: 1) Take 90 parts of water, add 0.5 parts of xanthan gum, and stir for 30 minutes until a uniform suspension is formed; 2) Add 30 parts of quartz sand and 10 parts of nano-calcium carbonate to the suspension base liquid, and stir at 800 r / min for 15 min to obtain a mixed suspension. 3) Slowly add 100 parts of curable resin-coated particles to the mixed suspension and stir at 400 r / min for 30 min until the particle surface is uniformly coated to obtain solid blockage agent.

[0057] The liquid and solid plugging agents obtained in Experiment 3 were tested for relevant properties, and the results are as follows: The flowability test results of the liquid plugging agent in the injection state are shown in Table 1: Table 1 As can be seen from the data in Table 1, the liquid plugging agent has a viscosity of ≤50mPa·s at room temperature, exhibiting good fluidity and meeting the construction requirements for deep penetration.

[0058] The gelation time and strength test results of the liquid plugging agent at different temperatures are shown in Table 2: Table 2 As can be seen from the data in Table 2, within the temperature range of 40-90℃, the gelation time is 20-120h, the viscosity after gelation is ≥58000mPa·s, and the elastic modulus is greater than the viscous modulus, indicating that the gel has solid elastic characteristics and can effectively block water channeling and generate stress shielding.

[0059] The results of the salt resistance stability test of the liquid plugging agent are shown in Table 3: Table 3 As can be seen from the data in Table 3, under the condition of mineralization ≤83890mg / L, the viscosity retention rate after 180 days is ≥90%, indicating that the liquid plugging agent has excellent salt resistance stability.

[0060] The test results of the shear resistance of the liquid plugging agent are shown in Table 4: Table 4 The porous media shearing method involves passing the liquid plugging agent through artificial cores with different permeabilities at varying flow rates and measuring the viscosity of the effluent. Table 4 shows that the liquid plugging agent exhibits strong resistance to mechanical shearing and porous media shearing, with a maximum viscosity loss of <4.8%, enabling it to maintain its performance and be successfully injected into deep formations.

[0061] The strength test results of the solid plugging agent are shown in Table 5: Table 5 As can be seen from the data in Table 5, after curing at 90℃ for 48 hours, the compressive strength is ≥13.9MPa, the flexural strength is ≥6.1MPa, and the permeability of the solidified body is ≤1.42mD, which meets the requirements for high strength and low permeability sealing.

[0062] The stability test results of the solid plugging agent are shown in Table 6: Table 6 As can be seen from the data in Table 6, the solid plugging agent has a temperature resistance of ≤250℃, and its performance retention rate is ≥94% under the conditions of immersion in 12% hydrochloric acid, immersion in 12% sodium hydroxide, and 2000pv water drive flushing, demonstrating excellent long-term stability. Example 1

[0063] Old well revamp: Water control and oil production work in synergy to achieve "increased oil production without increased water production". The first implementation of water shut-off fracturing technology was carried out on an old well in the Xinghe block of Ansai Oilfield. Before the treatment, the well produced 5.09 cubic meters of fluid with a water cut of 91.80% and produced 0.35 tons of oil. After the treatment, the well produced 8.3 cubic meters of fluid with a water cut of 27.3% and produced 5.02 tons of oil. The water cut decreased by 64.5 percentage points, and the daily oil production increased by 4.67 tons, which is a significant effect. Example 2

[0064] Seeking Production from New Wells: The plugging effect is stable and long-lasting, achieving "long-term water control and stable oil production increase". This integrated water plugging and fracturing technology was applied to a new high water-cut well in the Baibao block of the Shaanbei exploration area of ​​Changqing Oilfield. Due to the longitudinal development of natural fractures in the reservoir that connect to water bodies, the well faced the problem of high water cut in the early stage of production. After the measures were taken, the well produced 60.86 cubic meters of oil per day and 0 cubic meters of water per day during the oil trial period, with significant results.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high water cut oil well solid-liquid coupling pre-plugging water shutoff and fracturing process, characterized in that, Includes the following steps: 1) Injection of liquid plugging agent: Liquid plugging agent is injected into the water channel in the formation of the target oil well. The fluidity of the liquid plugging agent is used to allow it to penetrate into the deep part of the water channel and cross-link into a gel under formation conditions, thereby deeply sealing the water flooding channel of the old fracture and forming a stress shield in the area, providing a basis for subsequent secondary fracturing to achieve a change in direction. 2) Injection of solid plugging agent: After step 1), solid plugging agent is injected into the target formation and pushed as a post-slug to the far end of the sealing area, so that it solidifies under formation conditions to form a high-strength, low-permeability isolation layer, which strengthens the sealing strength of the water flooding channel, prevents the subsequent secondary fracturing fluid from entering the old fracture and scouring the liquid plugging agent, and forms a synergistic sealing system with the liquid plugging agent. 3) Secondary redirection fracturing: Fracturing operations are carried out under the action of a synergistic plugging system. By utilizing the stress shielding and the injected fiber temporary plugging agent, the hydraulic fractures are forced to redirect, forming new fractures in unused or poorly utilized oil layers.

2. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 1, characterized in that, The liquid plugging agent is a hydroponic gel, which is prepared through the following steps: 1) Add the designed amount of injection water to the mixing tank, and then slowly add the modified acrylamide-sodium acrylate copolymer dry powder at a ratio of 0.3%-0.5% while stirring; 2) Control the water temperature at 20-30℃ and stir continuously for 60-90 minutes until the polymer is completely dissolved; 3) Add 0.01%-0.02% sodium thiosulfate by volume of the injected water and continue stirring until homogeneous; 4) Add acetate-sodium acetate buffer solution to adjust the pH of the system to 6.5-7; 5) Let the polymer system stand for 2-4 hours to mature, and at the same time dilute the composite organic delayed crosslinking agent with water at a ratio of 1:(10-15) to obtain a crosslinking agent dilution solution; 6) The liquid plugging agent is obtained by mixing the polymer system and the crosslinking agent dilution at a volume ratio of 100:(2.5-5).

3. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 2, characterized in that, The preparation method of the modified acrylamide-sodium acrylate copolymer includes the following steps: 1) Add the following parts by weight of raw materials to the reaction vessel: 60-70 parts of acrylamide, 15-25 parts of sodium acrylate, 10-20 parts of 2-acrylamide-2-methylpropanesulfonic acid, and 400-450 parts of deionized water, and then stir and mix. 2) Adjust the pH of the system to 7-8 with sodium hydroxide solution, and then purge nitrogen gas into the system for 30-40 minutes to remove dissolved oxygen; 3) At 10-20℃, add ammonium persulfate (0.01%-0.05% of total monomers) and sodium bisulfite (0.01%-0.03% of total monomers) to the system sequentially, then continue to purge with nitrogen gas and continue the reaction for 5-8 hours. 4) Heat to 40-50℃ and keep warm for 2-4 hours to ensure the reaction is complete and obtain polymer blocks; 5) The modified acrylamide-sodium acrylate copolymer is obtained by drying, crushing and sieving the polymer block.

4. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 2, characterized in that, The preparation method of the composite organic delayed crosslinking agent includes the following steps: 1) Add 30-40 parts of deionized water to the reactor; 2) Slowly add 25-35 parts of zirconium oxychloride to deionized water and stir until dissolved; 3) Slowly add 20-25 parts of lactic acid and 5-10 parts of triethanolamine to the system, while controlling the reaction temperature to not exceed 40℃; 4) After the addition is complete, continue stirring and react for 2-3 hours; 5) Add 10-20 parts of deionized water to the system and stir until homogeneous.

5. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 1, characterized in that, The preparation process of the solid plugging agent includes the following steps: 1) Take 80-100 parts of clean water, add 0.4-0.6 parts of xanthan gum, and stir for 20-30 minutes until a uniform suspension is formed; 2) Add 25-35 parts of quartz sand and 8-12 parts of nano-calcium carbonate to the suspension base liquid, and stir at a speed of 700-800 r / min for 10-15 min to obtain a mixed suspension; 3) Slowly add 100 parts of curable resin-coated particles to the mixed suspension and stir at 300-400 r / min for 20-30 min until the particle surface is uniformly coated to obtain the solid blocker.

6. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 5, characterized in that, The quartz sand has a mesh size of 70-140 mesh, and the nano-calcium carbonate has a particle size of 50-100 nm.

7. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 5, characterized in that, The preparation process of the curable resin-coated particles is as follows: 1) Take 100 parts of granular aggregate with a particle size of 70-140 mesh, dry it at 100-120℃ to remove surface moisture, and cool it to room temperature for later use. 2) Take 0.5-1 part of silane coupling agent KH-550 and mix it with anhydrous ethanol at a mass ratio of 1:

4. Spray the coupling agent after mixing with ethanol evenly on the surface of aggregate particles and let it stand for 30 minutes. 3) Take 12-18 parts of phenolic resin, heat it to 70-80℃, and then take 2-3 parts of hexamethylenetetramine curing agent and mix it evenly with the resin. 4) Mix the resin mixture with the surface-treated granular aggregate until homogeneous; 5) Dry the coated particles at 90-100℃ until the resin particles no longer stick together, and you will get the curable resin coated particles.

8. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 1, characterized in that, The injection volume ratio of the liquid plugging agent to the solid plugging agent is 60:1, and the injection amount of the solid plugging agent accounts for 40% of the target fracture volume.

9. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 1, characterized in that, The injection of liquid plugging agent, the injection of solid plugging agent, and the secondary diversion fracturing are continuous operations that do not require tripping the tubing string.

10. The high water-cut oil well solid-liquid coupling pre-fracturing and water shut-off process according to claim 1, characterized in that, The aforementioned solid-liquid coupling pre-plugging fracturing technology for high water-cut oil wells is suitable for repeated fracturing stimulation of old high water-cut wells and for commissioning of new high water-cut wells.

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